Study On The Correlation Between Saliva Glucose And Blood Sugar,and Its High Sensitivity Detection

Non-invasive blood glucose monitoring can avoid the pain of puncture wounds caused by conventional invasive detection methods（including venous blood glucose,glycosylated hemoglobin,fingertip blood glucose and continuous blood glucose monitoring）,reduce the cost of detection,and avoid safety problems such as blood infection diseases.Literature shows that the glucose in saliva is closely related to blood sugar level.Meanwhile,saliva collection has the advantages of high safety,non-invasive,convenient and real-time,and has become an ideal marker for non-invasive blood sugar monitoring.However,the concentration of glucose is low（about1/100 to 1/50 of the blood sugar level）,and the composition of saliva is extremely complex.Due to the limited accuracy of commonly used enzymatic method,which leads to great differences in the correlation coefficients between saliva glucose and blood sugar,and even no correlation between the two.Therefore,in this work,a high-precision ion chromatography method was firstly established to detect the saliva glucose concentration,and applied this technology in clinical to study the relationship between saliva glucose and blood sugar.Secondly,in view of the problems of complex operation,time-consuming,difficult to popularize,etc.,so we focus on development of clinical quartz crystal microbalance（QCM,it belongs to the quality sensor,which has the advantages of high sensitivity,simple structure,easy integration,and real-time monitoring data,etc.）to detect saliva glucose.In order to solve the problem of low concentration of saliva glucose,a novel and efficient film preparation technique,UV press-assisted polymerization was developed to synthesize high quality phenylboric glucose sensitive films on the surface of QCM chip.Aiming at the problem of non-specific interference of protein and bacteria in saliva,antifouling phenylboronic acid microgels and superhydrophilic gels were synthesized on the surface of QCM chips.The innovation points and main research results of this work are as follows:1.Establish an ion chromatography method to detect the concentration of saliva glucose,and analyze its correlation with blood sugar level.（1）The protective column and the analytical column used for chromatography analysis were Carbo Pac PA20（3×30 mm）and Carbo Pac PA20（3×150 mm）.The elution were composed of ultra-pure water,250 mmol/L Na OH solution and 500mmol/L Na Ac solution.Gradient elution was performed,and pulse ampere detector was used to test.The results showed that the linear range of glucose was 0.04 to 0.12mg/L,the detection limit was 2μg/L,the mean relative standard deviation（the abbreviation is RSD）was 0.75%,and the mean recovery rate was 103.07%.（2）A total of 268 subjects were included in the clinical trial,including 146people with normal glucose metabolism（the abbreviation is NGT）and 122 patients with diabetes mellitus（the abbreviation is DM）.Fasting venous blood and saliva were collected,and the concentration of blood sugar and saliva glucose were measured by automatic biochemical analyzer and ion chromatograph.All data were analyzed and processed by Statistical Products and Services Solutions（the abbreviation is SPSS,version number is 19.0）.The results showed that the average levels of blood sugar,Hb A1c and saliva glucose in the DM group were all higher than those in the NGT group.When the concentration of saliva glucose was higher than cut-off points（the value were set at 10,15,20 and 25 mg/L,respectively）,there was a significant positive correlation between saliva glucose and blood glucose level,the correlation coefficients（the abbreviation is r）were 0.321,0.379,0.509 and 0.428,respectively,and all P<0.05.2.Preparation of saliva glucose sensor base on QCM.（1）To solve the problem of low saliva glucose concentration,UV press-assisted polymerization was developed to prepare ultra-sensitive boric acid hydrogel coated QCM chip.The hydrogel has dense structure,sufficient glucose binding sites and good stability.Combined with QCM detection,the detection limit of this method was as low as 3 mg/L and the detection range was 0～160 mg/L.The results of artificial saliva test showed that the glucose sensor had good reproducibility（RSD<10%,test times（the abbreviation is n）=10,p H=7.9）.（2）Aiming at the problem of non-specific interference of complex and high content of protein in saliva,phenylboric acid microgels QCM glucose sensor with antifouling function was designed.Specifically,microgel networks provide a large number of boric acid binding sites to amplify targeting glucose signals,and the amino acid layer and crosslinking layer wrapped in the microgel can effectively eliminate the influence of non-specific proteins in saliva.The designed anti-fouling QCM sensor has a good linear relationship with the frequency of displacement（the abbreviation is△F）in p H 6.8～7.5 and glucose concentration in the range of 0～40mg/L.Good resistance to both proteins（fibrinogen,bovine serum albumin,lysozyme,mucin）and organic molecules（urea,ascorbic acid,uric acid,creatinine,levodopa,glutathione）.At the same time,glucose（100,200,500 mg/L,respectively）in 50%diluted saliva(V_PBS:V_saliva=1:1)coule be detected.（3）Aiming at the problem of non-specific interference between complex and high-content bacteria and proteins in saliva,a superhydrophilic gels with both antibacterial and anti-protein properties were synthesized on the surface of QCM chips.The designed super-hydrophilic gel QCM sensor had a good linear relationship with△F in the range of p H 6.8～7.5 and glucose concentration range of 0～60 mg/L.The sensor had shown excellent antipollution effect on eight kinds of common proteins（bovine serum albumin,myoglobin,keratin,amylase,lysozyme,fibrinogen,lactoferrin,transferrin）and three kinds of bacteria（streptococcus mutans,epidermis,escherichia coli）in saliva.At the same time,glucose（0.5,1.0,1.5,2.0 mmol/L,respectively）in 50%diluted saliva(V_PBS:V_saliva=1:1)coule be detected.